Compositions

ABSTRACT

A composition comprises (i) from about 2 to about 50% by weight 1,1-difluoroethene (vinylidene fluoride, R-1132a), (ii) from about 2 to about 95% by weight difluoromethane (R-32), and (iii) 2,3,3,3-tetrafluoropropene (R-1234yf).

The present application is a continuation of U.S. patent applicationSer. No. 17/465,304, filed Sep. 2, 2021, which is a continuation of U.S.patent application Ser. No. 16/637,194, filed Feb. 6, 2020, which is thenational phase of International Application No. PCT/GB2018/052243, filedAug. 6, 2018, which claims priority to United Kingdom Patent ApplicationNo. 1712813.3, filed Aug. 10, 2017, the entireties of all of which areincorporated by reference herein.

FIELD

The invention relates to compositions, preferably to heat transfercompositions which may be suitable as replacements for existingrefrigerants such as R-410A.

The listing or discussion of a prior-published document or anybackground in the specification should not necessarily be taken as anacknowledgement that a document or background is part of the state ofthe art or is common general knowledge.

Mechanical refrigeration systems and related heat transfer devices suchas heat pumps and air-conditioning systems are well known. In suchsystems, a refrigerant liquid evaporates at low pressure taking heatfrom the surrounding zone. The resulting vapour is then compressed andpassed to a condenser where it condenses and gives off heat to a secondzone, the condensate being returned through an expansion valve to theevaporator, so completing the cycle. Mechanical energy required forcompressing the vapour and pumping the liquid is provided by, forexample, an electric motor or an internal combustion engine.

Residential and light commercial air-conditioning and heat pump unitsare commonly charged with the non-flammable refrigerant R-410A, amixture of R-32 (difluoromethane) and R-125 (pentafluoroethane).Although the use of this refrigerant results in high system efficiencyand hence low energy consumption, the greenhouse (or global) warmingpotential (GWP) of R-410A is high (2100, using the IPCC AR4 data set).

R-32 (difluoromethane) has been proposed as an alternative to R-410A.R-32 is classed as mildly flammable (“2L” using the ASHRAEclassification system). It offers comparable energy efficiency to R-410Ain appropriately designed equipment and has a GWP of 675.

However, R-32 has a number of disadvantages: its compressor dischargetemperatures are significantly higher than R-410A and its operatingpressures can also be higher than for R-410A. Compensating for thesehigher discharge temperatures, by for example using “demand cooling” orliquid injection technologies is possible. These can however reduce thecapacity and energy efficiency of the system. A further disadvantage ofR-32 is that its GWP (675) is still high when compared to the GWPs ofhydrofluoro-olefin refrigerants such as tetrafluoropropenes orhydrocarbons such as propane.

Binary blends of R-32 with R-1234yf (2,3,3,3-tetrafluoropropene) orR-1234ze(E) (E-1,3,3,3-tetrafluoropropene) and ternary blends of R-32,tetrafluoropropenes (either R-1234ze(E) or R-1234yf) and a thirdcomponent have also been proposed as alternative fluids. Examples ofsuch fluids include R-454B, which is a binary mixture of R-32/R-1234yf(68.9%/31.1%) with a GWP of 466, and R-452B, a ternary mixture ofR-32/R-125/R-1234yf (67%/7%/26%) with a GWP of 698. These fluids havereduced GWP compared to R-410A and can offer reduced dischargetemperature. However, their GWP values are similar to R-32 and stillhigh when compared to the GWPs of hydrofluoro-olefin refrigerants orhydrocarbons.

In looking for alternative low temperature refrigerants, several otherfactors must also be considered. Firstly, if the fluid is to be used asa retrofit or conversion fluid in existing equipment, or as a “drop-in”to new equipment using an essentially unchanged R-410A system design,then non-flammability is highly desired, as the existing design willhave been based on the use of non-flammable fluid.

If an alternative fluid is to be employed in a wholly new system design,then a degree of flammability may be tolerable, but the use of highlyflammable fluids may impose cost and performance penalties to mitigatehazards. Acceptable charge size (refrigerant mass) in a system is alsogoverned by the flammability classification of the fluid, with class 3fluids, such as ethane, being the most strictly limited. In this case aweaker flammability characteristic is highly desirable since it mayallow larger system charges.

Thirdly, the typical application of such fluids is in residual orcommercial air-conditioning and heat pump units, which are usuallylocated in buildings. It is therefore desirable to have acceptably lowtoxicity as a characteristic of the fluid.

Furthermore, the volumetric capacity (a measure of the cooling powerachievable by a given size of compressor) and energy efficiency areimportant.

SUMMARY

Thus, there is a need to provide alternative refrigerants havingimproved properties such as low GWP (so as to reduce the environmentalimpact of refrigerant leakage), yet possessing acceptable refrigerationperformance, flammability characteristics and toxicology. There is alsoa need to provide alternative refrigerants that may be used in existingdevices such as refrigeration devices with little or no modification.

More specifically, it would be advantageous to find refrigerant blendshaving comparable performance (capacity and energy efficiency, expressedas COP) to R-410A with compressor discharge temperature comparable tothat of R-452B or R-454A but with a GWP significantly lower than that ofR-32. As R-32 and R-454B are both considered weakly flammable blends(flammability class “2L” according to ASHRAE Standard 34), it would alsobe desirable that such lower-GWP blends would be of flammability class2L.

The subject invention addresses the above and other deficiencies, andthe above needs, by the provision of a composition comprising1,1-difluoroethene (R-1132a), difluoromethane (R-32),2,3,3,3-tetrafluoropropene (R-1234yf), optionally carbon dioxide (CO₂,R-744), and, optionally, 1,1,2-trifluoroethene (R-1123). Suchcompositions are referred to hereinafter as compositions of theinvention.

DETAILED DESCRIPTION

The compositions of the invention typically contain from about 1 or 2 or3 or 4 to about 60% by weight R-1132a. Advantageously, such compositionscomprise from about 1 or 2 or 3 or 4 to about 50% by weight R-1132a,such as from about 1 or 2 or 3 or 4 to about 40% by weight R-1132a, forexample from about 1 or 2 or 3 or 4 to about 30% by weight R-1132a.Conveniently, the compositions of the invention comprise from about 1 or2 or 3 or 4 to about 25% by weight R-1132a, such as from 2 to about 20%by weight R-1132a, for example 3 or 4 to about 20% by weight R-1132a.Preferably, such compositions comprise from about 5 to about 20% byweight R-1132a.

The compositions of the invention typically contain from about 1 toabout 99% by weight R-32 or from about 2 to about 98% by weight R-32.Advantageously, such compositions comprise from about 2 to about 95% byweight R-32, such as from about 3 to about 95% by weight R-32.Conveniently, the compositions of the invention comprise from about 5 toabout 90% by weight R-32, such as from about 5 to about 85% by weightR-32, for example from about 10 to about 80% by weight R-32. Preferably,such compositions comprise from about 15 to about 75% by weight R-32,such as from about 15 to about 70% by weight R-32.

The compositions of the invention typically contain from about 1 toabout 99% by weight R-1234yf or from about 2 to about 98% by weightR-1234yf. Advantageously, so such compositions comprise from about 2 toabout 90% by weight R-1234yf, such as from 5 to about 90% by weightR-1234yf. Conveniently, the compositions of the invention comprise fromabout 7 to about 85% by weight R-1234yf, such as from about 8 to about80% by weight R-1234yf. Preferably, such compositions comprise fromabout 10 to about 75% by weight R-1234yf, such as from about 10 to about70% by weight R-1234yf, for example from about 10 to about 65% by weightR-1234yf.

Conveniently, compositions of the invention comprise from about 1 toabout 60% by weight R-1132a, from about 1 to about 99% by weight R-32,and from about 1 to about 99% by weight R-1234yf. Such compositionstypically contain from about 1 to about 50% by weight R-1132a, fromabout 2 to about 97% by weight R-32, and from about 2 to about 97% byweight R-1234yf.

Conveniently, compositions of the invention comprise from about 2 toabout 60% by weight R-1132a, from about 1 to about 97% by weight R-32,and from about 1 to about 97% by weight R-1234yf. Such compositionstypically contain from about 2 to about 50% by weight R-1132a, fromabout 2 to about 96% by weight R-32, and from about 2 to about 96% byweight R-1234yf.

Advantageously, compositions of the invention comprise from about 1 toabout 40% by weight R-1132a, from about 5 to about 90% by weight R-32,and from about 5 to about 90% by weight R-1234yf; or from about 2 toabout 40% by weight R-1132a, from about 5 to about 90% by weight R-32,and from about 5 to about 90% by weight R-1234yf; or from about 2 toabout 40% by weight R-1132a, from about 4 to about 94% by weight R-32,and from about 4 to about 94% by weight R-1234yf.

Preferably, compositions of the invention comprise from about 3 to about20% by weight R-1132a, from about 10 to about 80% by weight R-32 andfrom about 10 to about 75% by weight R-1234yf; or from about 3 to about30% by weight R-1132a, from about 10 to about 91% by weight R-32 andfrom about 6 to about 87% by weight R-1234yf.

Conveniently, compositions of the invention comprise from about 5 toabout 20% by weight R-1132a, from about 20 to about 70% by weight R-32and from about 10 to about 65% by weight R-1234yf; or from about 4 toabout 25% by weight R-1132a, from about 15 to about 88% by weight R-32and from about 8 to about 81% by weight R-1234yf.

Any of the above described compositions may additionally contain carbondioxide (R-744, CO₂). Adding R-744 has the advantage of reducing theR-1132a in the vapour phase and hence reducing potential flammability ofthe vapour phase, but tends to increase compressor discharge temperatureand temperature glide.

When present, the compositions of the invention typically contain fromabout 1 to about 20% by weight CO₂. Preferably, such compositionscontain from about 2 to about 15% by weight CO₂. In one embodiment, thecompositions of the invention contain R-1132a and CO₂ in a combinedamount of from about 2 to about 50% by weight, such as from about 2 toabout 40% by weight, for instance from about 4 to about 30% by weight,e.g. from about 5 to about 20% by weight.

Any of the above described compositions may additionally contain1,1,2-trifluoroethene (R-1123). An advantage of using R-1123 in thecompositions of the invention is that it gives similar capacity to R-32but it has negligible GWP. By incorporation of a proportion of R-1123the overall GWP of a composition having similar capacity to R-410A maythen be reduced compared to an equivalent ternary R-1132a/R-32/R-1234yfcomposition at constant R-1132a and R-1234yf proportions. R-1123 mayonly safely be used as a diluted component in compositions of theinvention. The proportion of R-1123 in the compositions of the typicallyis such that the maximum molar concentration of R-1123 either in thecomposition of the invention as formulated or in its worst-casefractionated compositions (as defined in ASHRAE Standard 34 Appendix B)should be less than 40%.

When present, the compositions of the invention typically contain fromabout 1 to about 30% by weight R-1123; or from about 5 to about 30% byweight R-1123. Preferably, such compositions contain from about 5 toabout 20% by weight R-1123 such as from about 5 to about 15% by weight,for example from about 5 to about 10% by weight R-1123.

Alternatively, the compositions of the invention may contain less thanabout 8% or about 7% or about 6% or about 5% by weight R-1123, such asless than about 4% or about 3% by weight R-1132a, for example less thanabout 2% or about 1% by weight R-1123. Preferably, such compositions aresubstantially free of R-1123. Advantageously, the compositions of theinvention contain no (readily detectable) R-1123.

Any of the above described compositions may further contain ahydrocarbon. Advantageously, the hydrocarbon is one or more compound(s)selected from the group consisting of ethane, propane, propene,isobutane, n-butane, n-pentane, isopentane and mixtures thereof. Withoutbeing bound by theory, it is believed that, when present, the inclusionof ethane and/or an additional hydrocarbon compound may enhance oilmiscibility, solubility and/or return characteristics. Typically, thecompositions of the invention contain from about 1 to about 20% byweight hydrocarbon component, such as from about 1 to about 10% byweight, for example from about 1 to about 5% by weight.

In an embodiment, the compositions may consist essentially of the statedcomponents. By the term “consist essentially of”, we include the meaningthat the compositions of the invention contain substantially no othercomponents, particularly no further (hydro)(fluoro)compounds (e.g.(hydro)(fluoro)alkanes or (hydro)(fluoro)alkenes) known to be used inheat transfer compositions. The term “consist of” is included within themeaning of “consist essentially of”.

In an embodiment, the compositions of the invention are substantiallyfree of any component that has heat transfer properties (other than thecomponents specified). For instance, the compositions of the inventionmay be substantially free of any other hydrofluorocarbon compound.

By “substantially no” and “substantially free of”, we include themeaning that the compositions of the invention contain 0.5% by weight orless of the stated component, preferably 0.4%, 0.3%, 0.2% or 0.1% orless, based on the total weight of the composition.

All of the chemicals herein described are commercially available. Forexample, the fluorochemicals may be obtained from Apollo Scientific (UK)and carbon dioxide may be obtained from liquefied gas suppliers such asLinde AG.

As used herein, all % amounts mentioned in compositions herein,including in the claims, are by weight based on the total weight of thecompositions, unless otherwise stated.

By the term “about”, as used in connection with numerical values ofamounts of components in % by weight, we include the meaning of ±0.5% byweight, for example ±0.5% by weight.

For the avoidance of doubt, it is to be understood that the stated upperand lower values for ranges of amounts of components in the compositionsof the invention described herein may be interchanged in any way,provided that the resulting ranges fall within the broadest scope of theinvention.

The compositions of the invention have zero ozone depletion potential.

Typically, the compositions of the invention have a GWP of less thanabout 650, such as less than about 600, for example less than about 500.Preferably, the compositions of the invention have a GWP of less thanabout 480, such as less than about 450, for example less than about 400.

Typically, the compositions of the invention are of reduced flammabilityhazard when compared to R-1132a.

Flammability may be determined in accordance with ASHRAE Standard 34incorporating the ASTM Standard E-681 with test methodology as perAddendum 34p dated 2004, the entire content of which is incorporatedherein by reference.

In one aspect, the compositions have one or more of (a) a higher lowerflammable limit; (b) a higher ignition energy (sometimes referred to asauto ignition energy or pyrolysis); or (c) a lower flame velocitycompared to R-1132a alone. Preferably, the compositions of the inventionare less flammable compared to R-1132a in one or more of the followingrespects: lower flammable limit at 23° C.; lower flammable limit at 60°C.; breadth of flammable range at 23° C. or 60° C.; auto-ignitiontemperature (thermal decomposition temperature); minimum ignition energyin dry air or flame speed. The flammable limits being determinedaccording to the methods specified in ASHRAE-34 and the auto-ignitiontemperature being determined in a 500 ml glass flask by the method ofASTM E659-78.

In a preferred embodiment, the compositions of the invention arenon-flammable. For example, the compositions of the invention arenon-flammable at a test temperature of 60° C. using the ASHRAE-34methodology. Advantageously, the mixtures of vapour that exist inequilibrium with the compositions of the invention at any temperaturebetween about −20° C. and 60° C. are also non-flammable.

In some applications it may not be necessary for the formulation to beclassed as non-flammable by the ASHRAE-34 methodology. It is possible todevelop fluids whose flammability limits will be sufficiently reduced inair to render them safe for use in the application, for example if it isphysically not possible to make a flammable mixture by leaking therefrigeration equipment charge into the surrounds.

In one embodiment, the compositions of the invention have a flammabilityclassifiable as 1 or 2L according to the ASHRAE standard 34classification method, indicating non-flammability (class 1) or a weaklyflammable fluid with flame speed lower than 10 cm/s (class 2L).

The compositions of the invention preferably have a temperature glide inan evaporator or condenser of less than about 10K, even more preferablyless than about 5K, and even more preferably less than about 1K.

It is believed that the compositions of the invention exhibit acompletely unexpected combination of low-/non-flammability, low GWP,improved lubricant miscibility and improved refrigeration performanceproperties. Some of these refrigeration performance properties areexplained in more detail below.

The compositions of the invention typically have a volumetricrefrigeration capacity that is at least 80% of that of R-410A, such asat least 85% of that of R-410A. Preferably, the compositions of theinvention have a volumetric refrigeration capacity that is at least 90%of that of R-410A, for example from about 95% to about 130% of that ofR-410A.

In one embodiment, the cycle efficiency (Coefficient of Performance,COP) of the compositions of the invention is within about 7% of R-410Asuch as within 5% of R-410A. Preferably, the cycle efficiency isequivalent to or higher than R-410A.

Conveniently, the compressor discharge temperature of the compositionsof the invention is within about 15K of the existing refrigerant fluidit is replacing (e.g. R-410A or R-32, preferably about 10K or even about5K. Advantageously, the compressor discharge temperature of thecompositions of the invention is lower than that of R-32.

Conveniently, the operating pressure in a condenser containing acomposition of the invention is lower than that of the condensercontaining R-32.

The compositions of the invention are typically suitable for use inexisting designs of equipment, and are compatible with all classes oflubricant currently used with established HFC refrigerants. They may beoptionally stabilised or compatibilised with mineral oils by the use ofappropriate additives.

Preferably, when used in heat transfer equipment, the composition of theinvention is combined with a lubricant.

Conveniently, the lubricant is selected from the group consisting ofmineral oil, silicone oil, polyalkyl benzenes (PABs), polyol esters(POEs), polyalkylene glycols (PAGs), polyalkylene glycol esters (PAGesters), polyvinyl ethers (PVEs), poly (alpha-olefins) and combinationsthereof. PAGs and POEs are currently preferred lubricants for thecompositions of the invention.

Advantageously, the lubricant further comprises a stabiliser.

Preferably, the stabiliser is selected from the group consisting ofdiene-based compounds, phosphates, phenol compounds and epoxides, andmixtures thereof.

Conveniently, the composition of the invention may be combined with aflame retardant.

Advantageously, the flame retardant is selected from the groupconsisting of tri-(2-chloroethyl)-phosphate, (chloropropyl) phosphate,tri-(2,3-dibromopropyl)-phosphate, tri-(1,3-dichloropropyl)-phosphate,diammonium phosphate, various halogenated aromatic compounds, antimonyoxide, aluminium trihydrate, polyvinyl chloride, a fluorinatediodocarbon, a fluorinated bromocarbon, trifluoro iodomethane,perfluoroalkyl amines, bromo-fluoroalkyl amines and mixtures thereof.

In one embodiment, the invention provides a heat transfer devicecomprising a composition of the invention. Preferably, the heat transferdevice is a refrigeration device.

Conveniently, the heat transfer device is a residential or commercialair conditioning system, a heat pump or a commercial or industrialrefrigeration system.

The invention also provides the use of a composition of the invention ina heat transfer device, such as a refrigeration system, as hereindescribed.

According to another aspect of the invention, there is provided asprayable composition comprising a material to be sprayed and apropellant comprising a composition of the invention.

According to a further aspect of the invention, there is provided amethod for cooling an article which comprises condensing a compositionof the invention and thereafter evaporating said composition in thevicinity of the article to be cooled.

According to another aspect of the invention, there is provided a methodfor heating an article which comprises condensing a composition of theinvention in the vicinity of the article to be heated and thereafterevaporating said composition.

According to a further aspect of the invention, there is provided amethod for extracting a substance from biomass comprising contacting thebiomass with a solvent comprising a composition of the invention, andseparating the substance from the solvent.

According to another aspect of the invention, there is provided a methodof cleaning an article comprising contacting the article with a solventcomprising a composition of the invention.

According to a further aspect of the invention, there is provided amethod for extracting a material from an aqueous solution comprisingcontacting the aqueous solution with a solvent comprising a compositionof the invention, and separating the material from the solvent.

According to another aspect of the invention, there is provided a methodfor extracting a material from a particulate solid matrix comprisingcontacting the particulate solid matrix with a solvent comprising acomposition of the invention, and separating the material from thesolvent.

According to a further aspect of the invention, there is provided amechanical power generation device containing a composition of theinvention.

Preferably, the mechanical power generation device is adapted to use aRankine Cycle or modification thereof to generate work from heat.

According to another aspect of the invention, there is provided a methodof retrofitting a heat transfer device comprising the step of removingan existing heat transfer fluid, and introducing a composition of theinvention. Preferably, the heat transfer device is a refrigerationdevice, such as an ultra-low temperature refrigeration system.Advantageously, the method further comprises the step of obtaining anallocation of greenhouse gas (e.g. carbon dioxide) emission credit.

In accordance with the retrofitting method described above, an existingheat transfer fluid can be fully removed from the heat transfer devicebefore introducing a composition of the invention. An existing heattransfer fluid can also be partially removed from a heat transferdevice, followed by introducing a composition of the invention.

The compositions of the invention may also be prepared simply by mixingthe R-1132a, R-32, R-1234yf (and optional components such as R-744,R-1123, hydrocarbons, a lubricant, a stabiliser or an additional flameretardant) in the desired proportions. The compositions can then beadded to a heat transfer device (or used in any other way as definedherein).

In a further aspect of the invention, there is provided a method forreducing the environmental impact arising from operation of a productcomprising an existing compound or composition, the method comprisingreplacing at least partially the existing compound or composition with acomposition of the invention.

By environmental impact we include the generation and emission ofgreenhouse warming gases through operation of the product.

As mentioned above, this environmental impact can be considered asincluding not only those emissions of compounds or compositions having asignificant environmental impact from leakage or other losses, but alsoincluding the emission of carbon dioxide arising from the energyconsumed by the device over its working life. Such environmental impactmay be quantified by the measure known as Total Equivalent WarmingImpact (TEWI). This measure has been used in quantification of theenvironmental impact of certain stationary refrigeration and airconditioning equipment, including for example supermarket refrigerationsystems.

The environmental impact may further be considered as including theemissions of greenhouse gases arising from the synthesis and manufactureof the compounds or compositions. In this case the manufacturingemissions are added to the energy consumption and direct loss effects toyield the measure known as Life-Cycle Carbon Production (LCCP). The useof LCCP is common in assessing environmental impact of automotive airconditioning systems.

In a preferred embodiment, the use of the composition of the inventionresults in the equipment having a lower Total Equivalent Warming Impact,and/or a lower Life-Cycle Carbon Production than that which would beattained by use of the existing compound or composition.

These methods may be carried out on any suitable product, for example inthe fields of air-conditioning, refrigeration (e.g. low and ultra-lowtemperature refrigeration), heat transfer, aerosols or sprayablepropellants, gaseous dielectrics, flame suppression, solvents (e.g.carriers for flavorings and fragrances), cleaners, topical anesthetics,and expansion applications. Preferably, the field is refrigeration.

Examples of suitable products include heat transfer devices, sprayablecompositions, solvents and mechanical power generation devices. In apreferred embodiment, the product is a heat transfer device, such as arefrigeration device.

The existing compound or composition has an environmental impact asmeasured by GWP and/or TEWI and/or LCCP that is higher than thecomposition of the invention which replaces it. The existing compound orcomposition may comprise a fluorocarbon compound, such as a perfluoro-,hydrofluoro-, chlorofluoro- or hydrochlorofluoro-carbon compound or itmay comprise a fluorinated olefin.

Preferably, the existing compound or composition is a heat transfercompound or composition such as a refrigerant. Examples of refrigerantsthat may be replaced include R-410A, R454B, R-452B and R-32, preferablyR-410A.

Any amount of the existing compound or composition may be replaced so asto reduce the environmental impact. This may depend on the environmentalimpact of the existing compound or composition being replaced and theenvironmental impact of the replacement composition of the invention.Preferably, the existing compound or composition in the product is fullyreplaced by the composition of the invention.

The invention is illustrated by the following non-limiting examples.

EXAMPLES

Ternary Mixtures of R-1132a. R-32 and R-1234yf

A thermodynamic model was constructed to allow estimation of theperformance of compositions comprising R-1132a or CO₂ in a vapourcompression refrigeration or air conditioning cycle. The criticaltemperature of R-1132a is about 30° C. and that of CO₂ is about 31° C.;both are lower than the condensing temperatures experienced in manyapplications of R-410A, which could range from 30 to 60° C. Therefore, athermodynamic model was developed that is capable of predictingvapour-liquid equilibrium of mixtures at temperatures above the criticaltemperature of some components in the mixture.

The chosen model used the Peng-Robinson equation of state forcalculation of the mixtures' thermodynamic properties. The vapour-liquidequilibrium (VLE) of mixtures was correlated using the Peng-Robinsonequation of state coupled with the mixing rules of Wong and Sandler asdescribed in Orbey, H., & Sandler, S. (1998), Modeling Vapor-LiquidEquilibria: Cubic Equations of State and their Mixing Rules, Cambridge:Cambridge University Press, which is included herein by reference. Thistype of thermodynamic model has been used with success for modelling theVLE of refrigerant mixtures (Shiflett, M., & Sandler, S. (1998),Modeling Fluorocarbon Vapor-Liquid Equilibria using the Wong-SandlerModel, Fluid Phase Equilibria, 145-162, incorporated herein byreference) and for modelling VLE of mixtures where one of the species isabove its critical temperature (Valtz, A., Coquelet, C., & Richon, D.(2007), Vapor-liquid equilibrium data for the hexafluoroethane+carbondioxide system at temperatures from 253 to 297K and pressures up to 6.5MPa, Fluid Phase Equilibria, 179-185, incorporated herein by reference).The Wong-Sandler model also allows reliable prediction of mixture VLE athigher temperatures and pressures than those used to generateexperimental data used in regression of its mixture parameters, bycoupling a model of the free energy of the liquid phase to the equationof state parameters. This makes it suitable for the estimation of vapourcompression cycle performance for the contemplated mixtures.

In this work the Wong-Sandler mixing rules were used with the non-randomtwo-liquid (NRTL) model to represent the free energy of the liquidphase. The Peng-Robinson equation's parameters for each mixturecomponent were modified to use the temperature correlation of Mathiasand Copeman, so as accurately to represent the component vapourpressures.

The interaction parameters of the Wong-Sandler/NRTL model were regressedto experimental measurements of vapour liquid equilibrium for binarymixtures of R-1132a with CO₂, R-32 and R-1234yf. The experimentalmeasurements' temperature range used varied from −55 to +10° C. forR-1132a/CO₂ and R-1132a/R-32 mixtures, to −40 to +40° C. forR-1132a/R-1234yf mixtures. The data for these mixtures and for binarymixtures of R1234yf with R-32 and CO₂ were measured using astatic-synthetic equilibrium cell.

Literature data were also available for the VLE of R-32 with CO₂(Rivollet, F., Chapoy, C., Coquelet, C., & Richon, D. (2004),Vapor-liquid equilibrium data for the carbon dioxide(CO2)+difluoromethane (R32) system at temperatures form 283.12 to 343.25K and pressures up to 7.46 MPa, Fluid Phase Equilibria, 95-101,incorporated herein by reference) (Adams R A, Stein F P. (1971),Vapor-Liquid Equilibria for Carbon Dioxide-Difluoromethane System,Journal of Chemical Engineering Data, 1146-149., incorporated herein byreference) and for R-1234yf with CO₂ (Juntarachat, N. et al. (2014),Experimental measurements and correlation of vapor-liquid equilibriumand critical data for the CO₂+R1234yf and CO₂+R1234ze(E) binarymixtures, International Journal of Refrigeration, 141-152, incorporatedherein by reference) and were used in the parameter regression.

Cycle modelling was carried out using state points from the modellingmatrix proposed by AHRI's Low-GWP Alternative Refrigerants EvaluationProgramme. The conditions used are given in Table 1 below:

TABLE 1 Cycle conditions for R-1132a/R-32/R- 124yf ternary systemmodelling Cycle conditions for modelling R410A Mean condensertemperature ° C. 37.8 Mean evaporator temperature ° C. 4.4 Condensersubcooling K 5.6 Evaporator superheat K 5.6 Evaporator pressure drop bar0.00 Suction line pressure drop bar 0.00 Condenser pressure drop bar0.00 Compressor suction superheat K 0.00 Isentropic efficiency 70.0%

In order to validate that the thermodynamic model gave reasonableresults, a comparison was carried out by using the industry standardNIST REFPROP9.1 program to simulate cycle performance for R-410A. TheMexichem thermodynamic model was then used to calculate the cycleperformance. Results are shown in Table 2, below.

TABLE 2 Comparison of REFPROP and Mexichem thermodynamic model resultsResults REFPROP MEXICHEM COP 4.8 4.8 Volumetric capacity kJ/m³ 5999 5996Pressure ratio 2.5 2.5 Compressor discharge ° C. 66.6 69.3 temperatureEvaporator inlet pressure bar 9.2 9.3 Condenser inlet pressure bar 22.922.9 Evaporator inlet temperature ° C. 4.4 4.4 Evaporator glide (out-in)K 0.1 0.1 Condenser glide (in-out) K 0.1 0.1

Comparative calculations of the performance of R-32 and R-454B werefirst carried out using the model. The results are shown in Table 3below.

TABLE 3 Refrigeration performance modelling data of R-32 and R-454Brelative to R-410A Parameter Units R410A R32 R-454B Coefficient ofPerformance (COP) 4.85 4.89 5.06 Volumetric cooling capacity kJ/m³ 59966490 5823 Discharge temperature ° C. 69.3 88.6 74.9 Condenser pressurebar 22.9 23.5 21.1 Evaporator pressure bar 9.3 9.4 8.6 Pressure ratio2.45 2.51 2.46 Condenser glide K 0.2 0.0 1.4 Evaporator glide K 0.1 0.01.5 COP relative to reference 100% 101% 104% Capacity relative toreference 100% 108%  97% Discharge temperature 0 19.4 5.7 differencefrom reference GWP 2100 675 466

Next a series of compositions of R-1132a/R-32/R-1234yf ranging from5-20% R-1132a and 20-70% R-32 were analysed. The results are shown inTables 4-7 below. The compositions of each component are given in weightpercentages in these tables.

TABLE 4 Refrigeration performance modelling data forR-1132a/R-32/R-1234yf ternary system containing 5% R-1132a R-1132a 5 5 55 5 R32 30 40 50 60 70 R1234yf Parameter Units 65 55 45 35 25Coefficient of Performance (COP) 5.14 5.10 5.07 5.04 5.01 Volumetriccooling capacity kJ/m³ 4843 5288 5676 6011 6290 Discharge temperature °C. 65.2 68.3 71.2 74.1 77.2 Condenser pressure bar 17.8 19.4 20.8 22.022.9 Evaporator pressure bar 7.0 7.7 8.4 8.9 9.3 Pressure ratio 2.532.50 2.48 2.46 2.45 Condenser glide K 8.5 6.8 5.2 3.9 2.9 Evaporatorglide K 7.9 6.6 5.1 3.8 2.8 COP relative to reference 106% 105% 104%104% 103% Capacity relative to reference  81%  88%  95% 100% 105%Discharge temperature difference −4.0 −1.0 1.9 4.8 7.9 from referenceGWP 205 272 339 407 474 Refrigeration performance modelling data forR-1132a/R-32/R-1234yf ternary system containing 10% R-1132a R-1132a 1010 10 10 10 R32 30 40 50 60 70 R1234yf Parameter Units 60 50 40 30 20Coefficient of Performance (COP) 5.08 5.04 5.02 5.00 4.98 Volumetriccooling capacity kJ/m³ 5275 5724 6116 6452 6726 Discharge temperature °C. 67.4 70.2 72.9 75.7 78.7 Condenser pressure bar 19.6 21.2 22.6 23.824.6 Evaporator pressure bar 7.8 8.5 9.2 9.7 10.1 Pressure ratio 2.522.50 2.47 2.45 2.44 Condenser glide K 10.0 8.0 6.3 5.0 4.0 Evaporatorglide K 9.4 7.8 6.2 4.9 3.9 COP relative to reference 105% 104% 103%103% 103% Capacity relative to reference  88%  95% 102% 108% 112%Discharge temperature difference −1.8 0.9 3.6 6.4 9.5 from reference GWP205 272 339 407 474 Refrigeration performance modelling data forR-1132a/R-32/R-1234yf ternary system containing 15% R-1132a VDF 15 15 1515 15 15 R32 20 30 40 50 60 70 R1234yf Parameter Units 65 55 45 35 25 15Coefficient of Performance (COP) 5.04 5.02 4.99 4.97 4.96 4.94Volumetric cooling capacity kJ/m³ 5181 5702 6156 6553 6889 7157Discharge temperature ° C. 66.4 69.2 71.8 74.3 77.0 80 Condenserpressure bar 19.5 21.4 23.1 24.5 25.6 26.4 Evaporator pressure bar 7.78.5 9.3 10.0 10.5 10.9 Pressure ratio 2.55 2.51 2.48 2.46 2.44 2.42Condenser glide K 13.0 10.8 8.7 6.9 5.6 4.8 Evaporator glide K 12.0 10.58.8 7.1 5.7 4.9 COP relative to reference 104% 103% 103% 102% 102% 102%Capacity relative to reference  86%  95% 103% 109% 115% 119% Dischargetemperature difference −2.9 0.0 2.5 5.0 7.7 10.8 from reference GWP 138205 272 339 406 474 Refrigeration performance modelling data forR-1132a/R-32/R-1234yf ternary system containing 20% R-1132a VDF 20 20 2020 20 20 R32 20 30 40 50 60 70 R1234yf Parameter Units 60 50 40 30 20 10Coefficient of Performance (COP) 4.97 4.95 4.93 4.92 4.92 4.91Volumetric cooling capacity kJ/m³ 5597 6122 6584 6986 7319 7580Discharge temperature ° C. 68.1 70.7 73.0 75.4 78.0 81.1 Condenserpressure bar 21.4 23.3 25.0 26.3 27.4 28.2 Evaporator pressure bar 8.49.4 10.1 10.8 11.3 11.7 Pressure ratio 2.53 2.49 2.46 2.44 2.42 2.41Condenser glide K 13.6 11.1 8.9 7.2 6.0 5.3 Evaporator glide K 13.1 11.39.3 7.6 6.4 5.7 COP relative to reference 103% 102% 102% 101% 101% 101%Capacity relative to reference  93% 102% 110% 117% 122% 126% Dischargetemperature difference −1.1 1.4 3.8 6.1 8.8 11.9 from reference GWP 138205 272 339 406 474

Surprisingly, the results show that it is possible to formulate ternaryblends of R-1132a/R-32/R-1234yf that give acceptable performance whencompared to R-410A whilst achieving lower GWP than R-32 or R-454B.

Especially preferred compositions will be those that can be classed ashaving “2L” flammability and which can be used on a “drop-in” or “neardrop-in” basis in systems designed for R-410A. It is thought that suchcompositions should meet the following criteria:

-   -   Capacity of at least about 90% of R-410A    -   COP equivalent or higher to that of R-410A    -   Operating pressure in condenser equal or lower than that of R-32    -   Compressor discharge temperature lower than that of R-32    -   Temperature “glide” in evaporator and condenser less than about        10K    -   Worst-case composition burning velocity of less than 10 cm/s as        per ASHRAE Standard 34

Other compositions which offer acceptable operating pressure andflammability but which do not meet all of these criteria may also giveacceptable performance in suitably designed new equipment. For example,blends having volumetric capacity of less than 90% that of R-410A couldbe used by increasing compressor displacement or compressor speed.Blends having larger temperature glide than 10K could be used byemploying cross-counterflow heat exchanger designs of condenser and/orevaporator.

Blends which have good performance characteristics but which exhibitclass 2 flammability may also be used in systems where the charge sizeand application conditions make it safe for use.

The invention is defined by the following claims.

1. A composition comprising: (i) from about 2 to about 50% by weight1,1-difluoroethene (vinylidene fluoride, R-1132a); (ii) from about 2 toabout 95% by weight difluoromethane (R-32); and (iii)2,3,3,3-tetrafluoropropene (R-1234yf).
 2. The composition according toclaim 1, wherein the content of R-1132a is from about 2 to about 40% byweight.
 3. The composition according to claim 1, wherein the content ofR-1132a is from about 3 or about 5 to about 20% by weight.
 4. Thecomposition according to claim 1, wherein the content of R-32 is fromabout 5 to about 90% by weight R-32.
 5. The composition according toclaim 1, wherein the content of R-32 is from about 10 to about 80% byweight.
 6. The composition according to claim 1, wherein the content ofR-1234yf is from about 1 to about 96% by weight.
 7. The compositionaccording to claim 1, wherein the content of R-1234yf is from about 10to about 65% by weight.
 8. The composition according to claim 1,consisting essentially of from about 2 to about 40% by weight R-1132a,from about 4 to about 94% by weight R-32, and from about 4 to about 94%by weight R-1234yf.
 9. The composition according to claim 1, consistingessentially of from about 3 to about 30% by weight R-1132a, from about10 to about 91% by weight R-32 and from about 6 to about 87% by weightR-1234yf.
 10. The composition according to claim 1, consistingessentially of from about 4 to about 25% by weight R-1132a, from about15 to about 88% by weight R-32 and from about 8 to about 81% by weightR-1234yf.
 11. The composition according to claim 1, wherein thecomposition has: a. a higher flammable limit as measured in accordancewith ASHRAE Standard 34; b. a higher ignition energy as determined in a500 ml glass flask by the method of ASTM E659-78; and/or c. a lowerflame velocity as measured in accordance with ASHRAE Standard 34compared to R-1132a alone.
 12. The composition according to claim 1,wherein the composition has a volumetric refrigeration capacity that isat least 90% of that of R-410A, and/or wherein the composition has acoefficient of performance (COP) that is equivalent or higher to that ofR-410A; and/or wherein the composition has an operating pressure in acondenser equal to or lower than that of R-32, and/or wherein thecomposition has a compressor discharge temperature that is lower thanthat of R-32; and/or wherein the composition has a temperature glide inan evaporator or condenser of less than about 10K, preferably less thanabout 5K; and/or wherein the composition has a burning velocity of lessthan about 10 cm/s as measured by ASHRAE Standard
 34. 13. Thecomposition according to claim 1, further comprising a lubricant. 14.The composition according to claim 13, wherein the lubricant is selectedfrom mineral oil, silicone oil, polyalkyl benzenes (PABs), polyol esters(POEs), polyalkylene glycols (PAGs), polyalkylene glycol esters (PAGesters), polyvinyl ethers (PVEs), poly (alpha-olefins) and combinationsthereof, preferably wherein the lubricant is selected from PAGs or POEs.15. The composition according to claim 1, further comprising astabiliser.
 16. The composition according to claim 15, wherein thestabiliser is selected from diene-based compounds, phosphates, phenolcompounds and epoxides, and mixtures thereof.
 17. The compositionaccording to claim 1, further comprising a flame retardant.
 18. Thecomposition according to claim 17, wherein the flame retardant isselected from the group consisting of tri-(2-chloroethyl)-phosphate,(chloropropyl) phosphate, ti-(2,3-dibromopropyl)-phosphate,tri-(1,3-dichloropropyl)-phosphate, diammonium phosphate, varioushalogenated aromatic compounds, antimony oxide, aluminium trihydrate,polyvinyl chloride, a fluorinated iodocarbon, a fluorinated bromocarbon,trifluoro iodomethane, perfluoroalkyl amines, bromo-fluoroalkyl aminesand mixtures thereof.
 19. A heat transfer device containing acomposition of claim
 1. 20. The heat transfer device of claim 19,wherein the heat transfer device is a refrigeration device, and/orwherein the heat transfer device comprises a residential or commercialair conditioning system, a heat pump or a commercial or industrialrefrigeration system.
 21. A method for cooling an article, comprising:condensing a composition of claim 1, and thereafter evaporating thecomposition in the vicinity of the article to be cooled.
 22. A methodfor heating an article, comprising: condensing a composition of claim 1in the vicinity of the article to be heated, and thereafter evaporatingthe composition.
 23. A mechanical power generation device containing acomposition of claim
 1. 24. The mechanical power generation device ofclaim 23, wherein the mechanical power generation device is adapted touse a Rankine Cycle or modification thereof to generate work from heat.25. A method of retrofitting a heat transfer device, comprising:removing an existing heat transfer composition, and introducing acomposition of claim
 1. 26. The method of retrofitting a heat transferdevice of claim 25, wherein the heat transfer device is a commercial orindustrial refrigeration device, a heat pump, or a residential orcommercial air conditioning system, optionally wherein the heat transfercomposition is a refrigerant selected from R-410A, R-454B, R-452B andR-32.
 27. A method for reducing the environmental impact arising fromthe operation of a product comprising an existing compound orcomposition, the method comprising: replacing at least partially theexisting compound or composition with a composition of claim
 1. 28. Themethod for reducing the environmental impact of claim 27, wherein theuse of the composition of claim 1 results in a lower Total EquivalentWarming Impact, and/or a lower Life-Cycle Carbon Production than isattained by use of the existing compound or composition.